1. Field of the Invention
The present invention relates to a ferrule holding structure for an optical connector component for use in connection between fiber optic cables.
2. Description of the Related Art
In general, in an optical communication system, several types of optical connector components have been used for detachably connecting between one fiber optic cable and another fiber optic cable or other optical device. One example of such optical connector components is an optical attenuator that is disclosed in TOKKOHEI No. 5-45924. Such optical attenuator is designed to have optical connectors mounted on both sides thereof so that an optical signal is relayed and attenuated between those optical connectors.
One such conventional type attenuator 1 is illustrated in FIG. 4. Referring to this figure, the optical attenuator 1 includes a ferrule 2 for receiving a core optical fiber at the center thereof, a connection sleeve 3 for an attenuation film 61 affixed to an outer middle portion of the ferrule 2, a split sleeve 4 affixed to an outer rear end portion of the ferrule 2, a first plug frame 5 for surrounding and holding a front end portion of the ferrule 2, a second plug frame 6 for surrounding and holding an opposite rear end portion of the ferrule 2, and a housing member 7 for accommodating the first and second plug frames 5 and 6.
The ferrule 2 is made of some ceramic material such as zirconia and has an axially elongated cylindrical form on which the attenuation film 61 is deposited for attenuating the passage of light.
The connection sleeve 3 is made of some metal material such as copper alloy in the form of a hollow cylinder that is affixed to the ferrule 2 with an adhesive. A flange 8 is affixed on an outer peripheral of the ferrule 2 adjacent a front end of the sleeve 3. The flange 8 is made of metal and has predetermined number of grooves (not shown) formed on an outer surface thereof.
The split sleeve 4 is made of zirconia, for example, in the form of a hollow cylinder and is axially split to provide resiliency. The split sleeve 4 has a front end surface that is contact with the rear end surface of the connection sleeve 3, and an opposite rear end surface that is backwardly projected beyond the rear end surface of the ferrule 2.
The first plug frame 5 is made of some plastic material, for example, and it is generally in the form of a cubic in which a cylindrical cavity 9 is axially formed. An inner brim 10 is formed at the inner center portion of the first plug frame 5 and has keys provided at the rear end portion thereof in corresponding to the grooves in the flange 8. Thereby, the ferrule 2 having the connection sleeve 3 mounted thereon is prevented from falling off the front end of the attenuator 1. A first engagement portion 12 is formed on and projected from an outer surface of the first plug frame 5, and a protrusion 13 is formed on the rear portion of the first engagement portion 12. In addition, latch holes 14 are formed at positions opposite to each other on the rear portion of the first plug frame 5, and elongated cutouts (not shown) are also formed at another positions opposite to each other to extend from the rear end of the first plug frame 5.
The second plug frame 6 is made of some plastic material, for example, and includes, a cylindrical holding portion 16 in axial direction and a pair of thin plate-like resiliently deformable portions 17 that extend in cantilevered manner from the middle portion of the holding portion 16 toward the rear end of the attenuator 1. Each of the deformable portions 17 has its rear end portion inwardly projected to form a second engagement portion 18. The holding portion 16 has its outer surface on which latch projections 19 are formed at the positions corresponding to the latch holes 14, and its inner surface on which a shoulder 20 is formed at the middle portion thereof. The holding portion 16 further includes an inwardly projecting fall-off prevention portion 21 formed on the rear end portion thereof for preventing the ferrule 2 fixed to the split sleeve 4 from falling off the holding portion 16.
The housing member 7 is made of stainless steel, for example, and includes a front end portion 22 that is mated with an adapter (not shown) and a rear end portion 23 with which a plug (not shown) is mated. The front end portion 22 has such width that is smaller than that of the rear end portion 23 so that there is a difference in width produced therebetween. An opening 24 is provided on each of both sidewalls of the front end portion 22. Accordingly the first engagement portion 12 and the protrusion 13 may cause an axial floating movement along the openings 24. In addition, a key projection 25 is formed on an outer surface of the front end portion 22, and the corresponding guide recess 26 is formed in the sidewall of the rear end portion 23 so that it axially extends from the rear end thereof.
Now, the process of assembling the prior art optical attenuator 1 having the configuration as above will be described.
The connection sleeve 3 is affixed to the ferrule 2 with an adhesive. Then, the flange 8 is affixed so that it is contact with the front end surface of the connection sleeve 3. The split sleeve 4 is press-fitted so that it is contact with the rear end surface of the connection sleeve 3. Thereafter, the front end portion of the ferrule 2 having the connection sleeve 3, the split sleeve 4 and the flange 8 mounted thereon is inserted into the cavity 9 of the first plug frame 5 from the rear side thereof In this connection, the groove (not shown) on the flange 8 is mated with the key 11 of the first plug frame 5 so that the flange 8 abuts the brim 10. Then, the second plug frame 6 is inserted into the first plug frame 5 in such manner that the holding portion 16 of the second plug frame 6 surrounds the rear end portion of the split sleeve 4. Thereafter, the second plug frame 6 is further inserted until the latch projection 19 snaps into the latch hole 14 upon which the second plug frame 6 is coupled to the first plug frame 5. In this condition the ferrule 2 may floatingly be moved in the axial direction between the inner brim 10 of the first plug frame 5 and the shoulder 20 of the second plug frame 6. Finally the first and second plug frames 5 and 6 coupled together are inserted into the housing member 7 from the rear side thereof until the first engagement portion 12 and the protrusion 13 become received in the opening 24. Accordingly, the first and second plug frames 5 and 6 are held in the housing member 7, but they may floatingly be moved in the axial direction.
The optical attenuator 1 that is assembled in the manner as above is then connected as follows: When the front end portion 22 is mated with the adapter (not shown) so that the key projection 25 is received in the guide recess (not shown) of the adapter, then the first engagement portion 12 is engaged with the adapter. On the other hand, when the rear end portion 23 is mated with the plug (not shown) so that the key projection (not shown) of the plug is received in the guide recess 26, then the second engagement portion 18 is engaged with the plug. As the result, the plug is connected with the adapter through the optical attenuator 1.
However, the prior art optical connector components such as those including the optical attenuator 1 as described above are generally defective in that they need great number of parts and assembling steps, and involves many laborious works because of the sleeve 3 and the flange 8 made of metal. In addition, they are difficult to reduce the manufacturing cost.
Because an adhesive is used for affixing the connection sleeve 3 to the ferrule 2, any excessive amount of adhesive that has come out of the end of the connection sleeve 3 flows into between connection sleeve 3 and the split sleeve 4 or the flange 8, which may cause deterioration in precision of the length between the flange 8 and the split sleeve 4. Therefore, it is difficult to improve in precision of size and yield of the product in the prior art.
In view of the above an object of the present invention is to provide a ferrule holding structure that can reduce the number of parts and assembling steps, improve in precision of size and yield of the product, and reduce the manufacturing cost of the product.
To attain such object the present invention provides an optical connector component comprising a ferrule for receiving an end portion of a core optical fiber of a fiber optic cable, a flange mounted on the peripheral of the ferrule, and a one-piece plug frame for floatingly supporting the ferrule having the flange mounted thereon, in which the flange and the plug frame are provided with respective engagement portions that are mutually engaged, and in which the flange has such resiliency that it is reduced in diameter by a radial and inward force exerted through the engagement portions when the ferrule is inserted into the plug frame from one end thereof and the flange is restored to the original condition present before the insertion when the engagement portions are mutually engaged.
Preferably the flange is provided with an adhesive injection hole in the peripheral wall thereof and an enlarged diameter recess portion at one end thereof, and when an adhesive is injected into the adhesive injection hole after the flange is mounted on the ferrule, then the adhesive flows between the flange and the ferrule and reaches the enlarged diameter recess portion.
Furthermore, a clearance is produced between the flange and the ferrule, and when the ferrule having the flange mounted thereon is inserted into the plug frame from one end thereof, the flange is reduced in diameter due to the presence of the clearance. The flange is made of resin material.
Such construction of the present invention allows reduction in number of parts and assembling steps for the optical connector component, facilitated assembly works, improvement in precision of size, and reduction of manufacturing cost. In addition, there is substantially no possibility that an adhesive used for affixing the flange to the ferrule comes out of the end of the flange, which is effective to improve in precision of size and yield of the product.